when merging two loads, make sure to take the min of their alignment,

not the max.  This didn't matter until the previous patch because
instcombine would refuse to sink loads with differenting alignments.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85738 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 27 insertions, 1 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 4c6c2bb2ac..07681d15d8 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -10774,7 +10774,7 @@ Instruction *InstCombiner::FoldPHIArgLoadIntoPHI(PHINode &PN) {
     if ((LoadAlignment != 0) != (LI->getAlignment() != 0))
       return 0;
     
-    LoadAlignment = std::max(LoadAlignment, LI->getAlignment());
+    LoadAlignment = std::min(LoadAlignment, LI->getAlignment());
     
     // If the PHI is of volatile loads and the load block has multiple
     // successors, sinking it would remove a load of the volatile value from
diff --git a/test/Transforms/InstCombine/phi.ll b/test/Transforms/InstCombine/phi.ll
index 08d28b4de7..d5665f6b68 100644
--- a/test/Transforms/InstCombine/phi.ll
+++ b/test/Transforms/InstCombine/phi.ll
@@ -157,9 +157,35 @@ bb1:
 bb2:
   %E = phi i32 [ %C, %bb ], [ %D, %bb1 ]
   ret i32 %E
+; CHECK: @test9
 ; CHECK:       bb2:
 ; CHECK-NEXT:        phi i32* [ %B, %bb ], [ %A, %bb1 ]
 ; CHECK-NEXT:   %E = load i32* %{{[^,]*}}, align 1
 ; CHECK-NEXT:   ret i32 %E
 
 }
+
+define i32 @test10(i32* %A, i32* %B) {
+entry:
+  %c = icmp eq i32* %A, null
+  br i1 %c, label %bb1, label %bb
+
+bb:
+  %C = load i32* %B, align 16
+  br label %bb2
+
+bb1:
+  %D = load i32* %A, align 32
+  br label %bb2
+
+bb2:
+  %E = phi i32 [ %C, %bb ], [ %D, %bb1 ]
+  ret i32 %E
+; CHECK: @test10
+; CHECK:       bb2:
+; CHECK-NEXT:        phi i32* [ %B, %bb ], [ %A, %bb1 ]
+; CHECK-NEXT:   %E = load i32* %{{[^,]*}}, align 16
+; CHECK-NEXT:   ret i32 %E
+
+}
+